In recent years, there is a technology for performing encoding in units of words at the time of encoding data. In encoding performed in units of words, unlike compression using ZIP, encoding is not performed on a plurality of consecutive words. Thus, by performing encoding in units of words, it is possible to reuses a part of encoding data extracted, without processing anything, in an encoded state.
Here, when performing encoding in units of words, encoding is performed by using a static dictionary and a dynamic dictionary. The static dictionary is information in which codes are associated with words that frequently appear. If a word targeted for encoding is not present in the static dictionary, encoding is performed by registering the subject word in the dynamic dictionary and allocating a dynamic code to the word. For example, dynamic codes are allocated in the order in which words appear.
Patent Document 1: Japanese Laid-open Patent Publication No. 2014-204357
Patent Document 2: Japanese Laid-open Patent Publication No. 09-214352
Patent Document 3: Japanese Laid-open Patent Publication No. 10-260980
Patent Document 4: Japanese Laid-open Patent Publication No. 2004-013680